Re: rtc ds3232 call trace in kernel

[Akinobu Mita]

2016-04-18 15:15 GMT+09:00 Qianyu Gong <qianyu.gong@xxxxxxx>:
> Hi Akinobu,
>
>
>
> I got an rtc call trace when booting 4.6 kernel on our board and I found it
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> was caused by this patch:
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>
>
> commit fc1dcb0b39dbb10d3290f2fcd6e154670f699166
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> Author: Akinobu Mita <akinobu.mita@xxxxxxxxx>
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> Date:   Mon Mar 7 00:27:53 2016 +0900
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>
>
>     rtc: ds3232: use rtc->ops_lock to protect alarm operations
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>
>
>     ds3232->mutex is used to protect for alarm operations which
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>     need to access status and control registers.
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>
>
>     But we can use rtc->ops_lock instead.  rtc->ops_lock is held when most
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>     of rtc_class_ops methods are called, so we only need to explicitly
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>     acquire it from irq handler in order to protect form concurrent
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>     accesses.
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>
>
>     Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
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> Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx
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>
>
> The problem is that rtc->ops_lock would be accessed in ds3232_irq()
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> without being initialized as rtc_device_register() is called too late.

You have already identified the root cause of this issue.

> As Iâm not familiar with rtc things, could I just revert the patch or you
> already
>
> have a solution to this problem? Thanks in advance.

Could you check if the problem is resolved by moving the call of
devm_rtc_device_register() from the end of ds3232_probe() to just
before registering irq handler?